They can go out in the snow and rain-give them the choice, they know more about being a chicken than either you or me.
As for winter care-think DRY…and out of the wind…with a lot of ventilation. They can easily keep themselves warm if they are out of the wind and dry…even in a molt. They need fresh air, even if cold. It is much better than damp closed air for chickens.
As for frost bite, I never have trouble with it in bitter cold, because the moisture is frozen solid, and that keeps them dry. When I have it is with a chinook, everything thaws, and it gets sharply colder at night. Keeping the bedding clean and dry is the best prevention for frost bite. But in my experience it bothers me more than them.
MrsK